Manufacture of alloys

ABSTRACT

This invention relates to the introduction of a controlled quantity of a high melting metal component into a melt of a low melting base metal. This is effected by feeding a rod of the high melting component into the above melt, while the said rod is subjected to a sonic vibration, and at the same time, that portion of the rod protruding above the level of the melt is cooled. This melted ensures that the manufacture of alloys is effected with great accuracy, simplicity and economy.

United States Patent Pohlman et al. 1 Aug. 8, 1972 [54] MANUFACTURE OFALLOYS [56] References Cited [72] ll'lVBl'llOfSI Reimar Pohlman, 33 lmJohamestal- UNITED STATES PATENTS 51, Aachen; Klaus Groove, 2Reuschenberger Weg.404(), Neuss; 2,577,837 12/1951 Zifierer ..266/34 T Wlt Fi ht l, 63 s hi fb 3,273,212 9/1966 Garmy et al. ..75/65 Rnerstrasse, 4046 Buttgen-Vorst, all 3,275,787 9/1966 Newberry ..75/65 Rof Germany Filed: July 27, 1970 Appl. No.: 64,887

Related US. Application Data Division of Ser. No. 771,028, Oct. 28,1968, Pat. No. 3,592,636.

Foreign Application Priority Data Oct. 31, 1967 Germany ..G 51503 US.Cl. ..266/34 R Int. Cl ..C2lc 7/00 Field of Search..75/65 R, 93 R;266/33 R, 34 R,

Primary Examiner-Gerald A. Dost Attorney-Sughrue, Rothwell, Mion, Zinn &Macpeak ABSTRACT This invention relates to the introduction of acontrolled quantity of a high melting metal component into a melt of alow melting base metal. This is effected by feeding a rod of the highmelting component into the above melt, while the said rod is subjectedto a sonic vibration, and at the same time, that portion of the rodprotruding above the level of the melt is cooled.

This melted ensures that the manufacture of alloys is effected withgreat accuracy, simplicity and economy.

7 Claims, 6 Drawing Figures PA TENT EBAus a 1912 sum 1 or 3 fig. 2

PATENTEDAUB 81972 3,682 459 sum 3 or 3 r Fig.5

27 Fig. 6

MANUFACTURE OF ALLOYS The present application is a Divisionalapplication of Ser. No. 771,028, filed Oct. 28, 1968 for MANUFAC- TUREOF ALLOYS, by Reimar Pohlman et al issued as U.S. Pat. No. 3,592,636.

This invention relates to processes and apparatus for the introductionof controlled quantities of higher melting metal components into lowmelting base metals under the action of sonic vibrations.

The alloying of metals normally requires several process stops,especially since with higher melting components long dissolving timesare necessary, and accuracy of the desired alloying concentration cannotgenerally be attained in one melting process. The procedure is thusfirst to manufacture a pre-alloy of higher concentration and this isimmersed, either fluid or solid into a melting bath in which thefinished alloy is produced. In this, a control analysis of theconcentration of the alloy obtained is generally necessary, since metallosses, e.g., by burn off of the product, can occur. The manufacture ofalloys with very small concentrations of alloying components presents,for these reasons, special difliculties.

It has already been proposed to assist in overcoming the poor solubilityof high melting metals in low melting base metals by the action ofultrasound. It is, for example, known to manufacture metal alloys usingultrasound, in which the alloying components are converted by knownmeans into the liquid phase and finally vibrated with the object ofhomogenizing or dispersing the individual metallic components. In this,technique, the ultrasonic generator either engages on the wall of themelting vessel or dips into the melt itself.

It is also known to excite the melt itself, or the crucible, to highfrequency sonic vibrations by electromagnetic or electrodynamic methods.Low frequency vibration generators for melts are also known, which workin the audible region or act by the generation of shock waves on thesurface of the melt.

A method for the homogenization of a melt by ultrasonic excitement hasalso been described in which at least one of the fluid alloy componentsis blown into the other component or components by a pipe or nozzlearrangement. Finally, attempts have been made to build a body ofalloying metal into the floor of a melting vessel so that on excitementby ultrasound of the fluid melt surrounding it, it is dispersed ordissolved. It has also been proposed, without the use of ultrasound, tomake possible a one-step alloying process by introducing a measuredamount of fluid alloying metal into the base metal by means of specialapparatus.

The known processes of ultrasonic treatment of metal melts are intendedprimarily to achieve a reduction in the grain size of the structure.They are neither designed for, nor suitable for, effecting a controlledadjustment of the desired content of higher melting metal component inlower melting base metal.

It is an object of the present invention to provide a process and anapparatus, which enable the accurate manufacture of metal alloys in oneprocess step, without the use of pre-alloys being necessary, and wherebyan accuracy may be achieved which makes control analysis prior tocasting unnecessary. The invention has for its special purpose that ofenabling an introduction or exact dosing of alloying components of highmelting point into a base metal of low melting point in simple andeconomic fashion.

According to the present invention there is provided a process forintroducing a controlled quantity of a high melting metal component intoa melt of a low melting base metal which comprises feeding a rod of thehigh melting component into the said melt while subjecting the said rodto sonic vibration and at the same time cooling the rod which extendsabove the surface of the melt. According to a further feature of theinvention the rate of cavitation-produced solution of the metal rod thusachieved is controlled by adjustment of the depth of immersion of therod in the melt and by adjustment of the exciter frequency of anoscillation generator used to provide the sonic vibration.

According to a particular embodiment of the process according to theinvention, during the immersion of the rod, the excitation frequency ofthe vibration generators is automatically made to be the naturalfrequency of the vibration system, varying during solution, of the rod.

As sonic vibrations, ultrasonic vibrations are preferred, and theinvention will therefore be explained especially with reference to theuse of ultrasonic vibrations.

In the process according to the invention at least the lowest part ofthe vibration system is constituted by a rod of the metal to beintroduced, which on excitation with a definite ultrasonic energydissolves on immersion in the melting bath, the solution of the materialof the rod caused by cavitation being so controlled that an optimumdissolution velocity and a regular dissolution of the immersed portionof the rod are obtained. The control of various factors influencing thevibration treatment makes possible a large scale use of the process,from which it follows, in an economic fashion, ie in a short time, thatreproducible results of greater accuracy can be obtained.

By the immersion of the rod, which constitutes a part of the ultrasonicsystem, the rod itself tends to become very strongly heated, as a resultof its high thermal conductivity. This circumstance causes an increasein the damping of the vibrations, with consequent reduction in thesolution velocity. By shortening the rod as a result of dissolution, thenatural frequency of the whole system changes, and this again reducesthe solution velocity. It is optimally desirable so to control thesolution of the immersed rod, that the rod shortens itself at a constantcross-section and that metal removal takes place only at the face of theend of the rod. Without such control there is a tendency for metal to beremoved from the lateral surface(s) of the rod and this can lead topieces of the rod breaking away and either sinking or floating in themelt as not yet dissolved compact pieces of metal.

When this occurs accurately dosed additives of the rod metal areimpossible to achieve.

Surprisingly, success has now been obtained, by the process of thepresent invention, in the control of the foregoing contrary influenceson the direct vibrations of the metal to be introduced, so that amaximum dissolving power of the metal, with a high rate of removal and aminimum alloying time, can be obtained, and so that the process iseffective for large-scale use. In the process of the present inventionthe higher melting metal component is introduced from above into themelt of the lower melting component, as an automatically tunedultrasonically excited vibration element,

cooled until just above the melt surface, with a drive corresponding tothe solution rate, and is dissolved therein.

The intensity of the ultrasonic excitation is of great importance. In apractical embodiment there is used for carrying out the process, anapparatus, the essential components of which consist of a compoundtodshaped vibration system, which includes a rod,

' preferably of several half-wavelengths long, of especially lowacoustic damping, and integrally connected thereto, a similarlyrod-shaped piece of the metal to be vibrated and an adjustable advancingdevice. The compound rod-shaped vibration system is held at two pointsin as damping-free a way as possible, and is cooled in the workingposition to just above the melt surface. By this construction, it iseffected that in the rod of several half-wavelengths length of speciallylow acoustic damping, substantially the whole of the ultrasonic power isled, substantially without loss to the shorter piece of the metal,connected to its end, which is to be vibrated.

Preferably, the compound vibration system is excited with the aid of anultrasonic exciter, intensively at its natural frequency, and so thatthe rod is led in a vertical guide by means of a infinitely variableregulatable drive into the lower melting components in molten state,from above, with a speed which corresponds to the dissolution speed ofthe metal of the rod.

Since the ultrasonically excited vibration system shortens duringrunning, by dissolution of the metal of the rod, and thus the naturalfrequency increases by the same degree, the rod of length severalhalf-wavelengths is suitably provided at the excitation end with apickup, which controls the high frequency generator serving for theexcitation in such fashion that the excitation frequency of thegenerator automatically follows the varying natural frequency of thevibration system. The ultrasonic excitation thus remains constantdespite the dissolution and shortening of that part of the rod dippinginto the melt.

According to another embodiment of the invention, the'excitationfrequency can also be controlled by a time or weight regulated device,which for a constant dissolution velocity also shortens the vibrationelement with a constantly maintained speed. The control of frequency canresult in simple fashion from the constant decrease in the weight orbuoyancy of the vibration element dipping into the melt.

The dissolution velocity of the metal of the rod increases, for a givensonic power, with increasing temperature of the metal of the rod and ofthe surrounding melt of base metal. On the other hand, however, theultrasonic transfer in the metal of the rod decreases with risingtemperature, so that insufficient sonic power is obtained at the face ofthe rod. In order to obtain an optimum dissolution velocity a welldetermined cooling of the rod, and therewith an optimum temperaturereflection at the face, is of decisive importance. In order to obtain anespecially high dissolution velocity, this material-dependenttemperature reflection should be kept as high and as constant aspossible.

This requirement can be realized by carrying out the process accordingto the invention so that the melt of base metal or the rod of the metalto be introduced are constantly and regularly moved relative to oneanother, in that for example, the vibrated rod is introduced into themelt in an electric induction furnace. A device can also be providedwhich allows a reciprocatory or circular movement of the immersed rod.

The process of the present invention and an embodiment of apparatus foruse therein is illustrated by the accompanying drawings.

In FIG. 1 of the drawings there is illustrated an example of anapparatus according to the invention.

A sonic or magnetostrictive ultrasonic generator is designated 1, whichis surrounded by a housing la, and which, for example, can operate inthe region between 5 and 60 kc/s. It is rigidily connected to a rod 2 oflength greater than half a wavelength, to the lower end of which arod-shaped piece 3 of an alloy metal to be vibrated is attached, e.g.,screwed to the rod 2, as is indicated by 18. The resulting compositeultrasonically excited vibration system can be driven via a spindle 4with the aid of a drive 5, driven by an electric motor and adjustableinfinitely variable, on sliding collars 6 along a vertical guideway 7(having three columns), into the melt 8, or, after ending of the processdriven out again in fast drive. On the excited end of rod 2 there isattached a pickup 9, which can control the high frequency excitationgenerator.

The whole apparatus is mounted on the lid 10 of a melting crucible l1and extends through an opening in the lid 10 into the melting chamber ofthe crucible 11, the end of the rod 3 of the alloy metal dipping intothe melt of base metal 8. The ultrasonic exciter 1 is sprayed with acooling agent such as cooling water by a spray 12. If necessary, it canalso be cooled by the use of a gaseous cooling agent. The spray coolingprovided is essentially more advantageous than, for example, aconventional immersion cooling in water, because in the latter a greatdeal of the acoustic power generated is led away to the surroundingwater and housing, which is not the case in a spray process. Therodshaped sonic transmitter 2 is led through into the housing 1 or bymeans of or through an opening having an elastic seal 13. The seal 13can, for example, consist of a rubber ring, and is on the one handespecially poor in damping and thus removes almost no energy from thevibrating system, and on the other hand allows the reliable collectionof the cooling water, which can be led away via a pipe 14.

A further spray 12 is provided for trapping the heat conducted up fromthe melt 8 and the radiated heat, which is arranged in a vessel 15surrounding the joint between rod 2 and rod 3, by means of which thewater running away can be caught by a holder and seal 13. A suction tube14 serves to maintain the water level low, in order to avoid ultrasonicdissipation in the vessel 15. The vessel 15 is surrounding by a polishedreflective housing 16, and at its base is isolated from the housing 16by means of an intermediate asbestos ring 17, so that vboth heatradiation and heat conduction are greatly diminished.

In the apparatus according to the invention, thermal differences betweenthe metal rod 3 and the rod 2 are avoided by cooling of the joint withwhich the rod 3 of the alloying metal is acoustically rigidly joined tothe rod 2, so that the acoustic transfer at this point is held veryconstant.

An especial advantage of the apparatus according to the inventionconsists in that each part of the system which is important for goodtransfer of the high ultrasonic power remains cool and thus free ofdamping, despite the heat lost from the ultrasonic exciter from aboveand the heat conducted away from the melt.

A further advantage of the apparatus according to the invention can beseen in that a large relative change of the rod 3 introduced into thebase metal melt, results in only a small relative change, and thus acontrollable frequency change of the whole vibration system, consistingof the ultrasonic exciter 1, the vibration transmitter 2 and the rod 3.

The rod 3 can be constructed in various ways. The rod can be solid, orin some cases hollow. The rod can consist of a two or more alloycomponents. Further, particular sections or annuli of the alloying metalrod can consists of different materials.

FIG. 2 shows schematically the circuit principles of automatic frequencycontrol for an ultrasonic generator. The ultrasonic generator isdesigned 1 and a rod more than several half wavelengths long serving asvibration conductor is designated 2, to the end of which is joined a redshaped piece of alloying metal to be vibrated (here not shown). A pickup9 is fixed to the excited end of rod 2. The pickup 9 (electromagnetictransducer) transmits electrically the feed back voltage taken from therod 2 to the device 19 for automatic resonance tuning. In device 19 thefeedback voltage is amplified, before it is led to the high frequencygenerator 20, and the phase is corrected by a phase adjuster, so thatthe high frequency excitation and the ultrasound oscillate in phase.

In FIGS. 3 to 6 there are illustrated 4 rod pieces of vibrated, or to bevibrated, alloying metal in transverse section.

In FIG. 3 the rod piece 21 of alloying metal has a thread 18 on itsupper end, which can be screwed into a rod 2 serving as vibrationconductor (FIG. 1). At its lower face 22, metal is dissolved from rodpiece 21 in a metal melt by the action of the ultrasonic vibrations. Theface 22 is almost evenly worn away, and shows only a rough surfacecaused by theaction of cavitation consisting of many small craters. Therod piece 21 is, according to the process of the invention, regularlycooled down to just above the molten melt.

In FIG. 4 there is shown a corresponding rod piece 23 of alloying metal,as is obtained by dipping the rod piece of alloying metal excited byultrasonic vibrations without the application of cooling. It is clearlyevident that the metal removal at the face 24 is wholly irregular.

FIG. 5 shows a rod piece 25 which is constructed from two differentalloying metals. The rod piece 25 has an outer sleeve portion 26 of analloy X and a core piece 27 of an alloy Y.

FIG. 6 shows a rod piece 28 of alloying metal which is hollowlyconstructed. The upper end of the tubular rod is closed and bears thethread 18, which is screwable into the rod 2 which acts as a vibrationconductor.

The advantages of the method the invention are multiple: It allows themanufacture, as mentioned above, of alloys in which the great differencebetween the melting points of the alloy components would lead inconventional alloying to an uneconornically high bumoff, and it achievesthis without the use of protective gas, which substantially eases theworking conditions. Additionally, the process according to the inventionallows an excellent control of the dosage of the rod metal, especiallywhen the closely controllable apparatus described is used. This dosageis accurate since both the time of vibrating, and the intensity of theultrasonic excitement, can be adjusted to zero, and without vibrationthe higher melting component practically does not dissolve in the lowermelting component over a short period of time. On the basis of thisexact dosage possibility, there appears the further advantage that thenormally necessary analysis of the pre-prepared alloy can be avoided.The process makes it possible to establish a very high degree ofhomogeniety and to obtain very fine and regular dispersions, even withmetals of very different density.

The process and apparatus according to the present invention are thussuitable for accurate and rapid alloying, especially for small alloyingconcentrations. In the known alloying art, one is compelled afteralloying a small concentration of alloying metal, e.g., a concentrationof less than 1 percent, to take a test for control analysis prior topouring the melt, wherein one strives toward the lower limit of contentin the base metal, in order, if necessary to be able to correct theconcentration by additional alloying. However one generally proceeds insuch fashion that one first manufactures a pre-alloy of higherconcentration, casts this alloy to slabs or bars, in order then in themanufacture of the final alloy, to achieve an accurate end alloy withthe aid of the pre-alloy slabs. However, control analysis before castingis still not unnecessary, since varying metal losses can arise,especially in multi-stage alloying processes.

Compared to this, by the application of the present invention, thedirect and accurate manufacture of alloys is made possible, without thediversion of pre-alloys, alloying corrections and subsequent analysishaving to be taken. Thus, for example, rods can also be alloyed into abase melt by direct vibration, which consists of one metal alloy or ofseveral metals put together in sections, so that a multicomponent alloycan be manufactured in one process. Especially for the NE- metals, e.g.,zinc, even the smallest alloying concentrations, from a few hundredthsto a few tenths of a per cent, may have a pronounced effect on theproperties. Thus, for example, the ageing resistance of zinc-copperalloys can be importantly influenced by an iron or titanium content of0.02 percent.

The following example will serve to illustrate the invention.

EXAMPLE This Example illustrates the manufacture of a zinc alloy of purezinc with 0.15 percent titanium and 0.60 percent copper.

In the screw hole of the exciter rod 2 of an apparatus accordingto thedrawing there was screwed a rod of titanium of diameter 50 mm having oneend threaded. In the same way, a correspondingly prepared rod of copperof diameter 50 mm was joined to the exciter rod 2 of a second apparatus.Both units of apparatus were at the same time inserted with theiralloying rods of titanium and copper into a melt of pure zinc, a chargeof 300 kg of which has been heated to a temperature of 600 C. in anelectric induction furnace, the distance of the surface of the melt fromthe floor of the vessel being a few centimeters. The advance rate of thealloying rods 2 was set at 4 mm per minute. The original frequency ofthe ultrasonic exciter amounted to 20 kc/s, the average intensity to10.7 W/cm. In operation, the exciter frequency was matched to thevarying natural frequency of the vibration system 1,2,3.)

After a vibration time of 12 minutes, the apparatus with the titaniumrod was removed from the melt, and after a'time of 24 minutes that withthe copper rod was removed. Thereafter the contents of the furnace wereteemed, cast to rolling slabs, and these rolled out to bands. Analysisgave an accurate content of the alloy required, of 0.60 percent copperand 0.15 titanium, and the technological properties of the sheet metalmade from this alloy were found to be completely homogeneous.

The rods illustrated in FIG. 3 and 4 consist, for example, of titaniumwith a purity of 99.4 percent Ti and 0.25 percent Fe and are suitablefor the manufacture of a zinc-titanium alloy.

For manufacture of a multicomponent alloy, the rods in FIGS. 3 and 4 canconsists, for example, of a nickelchromium alloy with 76 percent nickeland 15 percent chromium.

The rod in FIG. 5 consists, for example, of a sleeve portion 25 of purealuminum with a purity of 99.5 percent Al, while the core is constructedof magnesium with a purity of 99.8 percent Mg. This rod is provided forthe manufacture of a zinc-alurninum-magnesium finished alloy.

The rod of FIG. 6 consists, for example of magnesium with a purity of99.8 percent and is tubularly constructed, in order, for example, toattain very precise dosages by means of a decreased rod face area, andalso, if necessary, to serve as a bell filled with protective gas.

We claim as our invention:

1. Apparatus for introducing controllable quantities of a high meltingmetal component with a melt of a low melting base metal which comprisesa vibration generator, a vibration transmitting element of lengthseveral half-wavelengths of the vibration and of low acoustic dampingattached to the vibration generator, means at the end of said elementremote from the vibrator for releasably securing thereto a rod of highmelting metal means for lowering the assembly to immerse the end of therod so attached into a melt of molten metal, said means including aspeed regulation device and means for cooling a rod so attached in theregion above the level to which the said rod is immersed.

2. Apparatus according to claim 1 wherein the assembly of vibrationgenerator, vibration transmitting element, and rod when attached ismounted for vertical movement in guides provided with elastic sealsserving to minimize damping of the vibratory system.

3. Apparatus according to claim 1 wherein the cooling means isconstructed as a fluid spray.

4. Apparatus according to claim 1 wherein the connection point betweenvibration transmitting element and attached metal rod is surrounded by ahousing which extends to just above the surface of the melt.

5. Apparatus according to claim 1 which includes a pickup for automaticcontrol of the excitation frequency in dependence on the varying naturalfrequency of th 1 'b ti l kgga r hth s $23 355: to claim 1 whichincludes a UNITED STATES PATENT @FFICE QERTIFICATE OF CQRREUHQN PatentNo. 9 I Dated August 972 Reimar POHLMAN et 2.1

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In The Heading:

The name of the Assignee was omitted. Should read:

--Assignee: Groove & Welter, Neuss, Germany-- Signed and sealed thisl0th day of April 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents "JRM PO-IOSCI (IO-69) USCOMM-DC 60376-P69 U.S. GOVERNMENTPRINTING OFFICE: I565 O-356-334

2. Apparatus according to claim 1 wherein the assembly of vibrationgenerator, vibration transmitting element, and rod when attached ismounted for vertical movement in guides provided with elastic sealsserving to minimize damping of the vibratory system.
 3. Apparatusaccording to claim 1 wherein the cooling means is constructed as a fluidspray.
 4. Apparatus according to claim 1 wherein the connection pointbetween vibration transmitting element and attached metal rod issurrounded by a housing which extends to just above the surface of themelt.
 5. Apparatus according to claim 1 which includes a pickup forautomatic control of the excitation frequency in dependence on thevarying natural frequency of the whole vibration system.
 6. Apparatusaccording to claim 1 which includes a weight dependent measuring devicefor determining the vibration time for the metal rod.
 7. Apparatusaccording to claim 1 which includes a stop contact for determining thevibration time for the metal rod.